1. Field of the Invention
This invention relates to the field of optics systems, and more specifically to systems for generating information storing holograms.
2. Background of the Related Art
The use of optical systems to generate holograms is generally known, as is the use of crystals in such an optical system. Examples of prior devices are as follows.
U.S. Pat. No. 3,296,594 shows the storage of a plurality of images in a bleachable crystal using an object and a reference beam. The focus position of the reference beam is changed for each image to thereby vary the area of storage within the crystal. In order to readout the stored images, the position of the reference beam is changed to the desired readout position, and the thus generated image is read out.
U.S. Pat. No. 3,782,802 describes the bulk storage of phase holograms in a ferroelectric crystal. The crystal has a hysteresis curve. The application of an initial voltage establishes a remnant state for the crystal. An object beam and a reference beam are used to write a hologram in the crystal when the voltage applied to the crystal is zero. This write period is followed by a nonillumination period during which the hologram is "fixed" by the application of a reverse polarity voltage. Thereafter, the reference beam is reapplied to the crystal.
U.S. Pat. No. 3,892,465 describes the writing of holograms to a ferroelectric crystal wherein electric fields of different values are applied to the crystal during writing and reading of the holograms.
U.S. Pat. No. 4,063,795 describes an electro-optic holographic storage device having a ferroelectric crystal whose opposite surface electrodes are shorted. A reference beam and an object beam write a hologram to the crystal with zero phase shift applied to the reference beam. In order to erase this hologram, the hologram is rewritten using a 90 degree phase shift in the reference beam.
U.S. Pat. No. 4,878,717 provides a liquid crystal variable reflectance device that enables the writing of holograms from a computer to a holographic plate. The various images to be written are provided by a computer to the liquid crystal to thereby control its reflective state as a function of the image. The object beam then reflects off of the liquid crystal to the holographic plate, where interference with a reference beam enables a hologram to be written.
U.S. Pat. No. 5,206,674 describes a light intensity amplifier wherein a low intensity light is modulated by a liquid crystal. This modulated low intensity light is presented to a photorefractive crystal along with an unmodulated high intensity beam. The output of the photorefractive crystal is a modulated high intensity beam.
The publication SCIENTIFIC AMERICAN, June 1993 at page 140 describes the use of photorefractive materials to store holograms.
The present invention utilizes a pixelated liquid crystal structure. U.S. Pat. Nos. 4,941,735, 5,073,010 and 5,177,628, incorporated herein by reference, show such a pixelated structure. Above-noted U.S. Pat. No. 5,073,010 also shows the use of a semiconductor substrate adjacent to a ferroelectric liquid crystal layer.
The present invention utilizes a ferroelectric liquid crystal. U.S. Pat. No. 4,367,924, incorporated herein by reference, discloses such a liquid crystal.
While prior devices as exemplified above are generally useful for their limited intended purposes, the need remains in the art for a programmable hologram generator comprising a layered structure of a VLSI chip, a reflective ferroelectric liquid crystal that is physically disposed on the VLSI chip, and a photorefractive crystal that is physically disposed on the liquid crystal, wherein programming of the VLSI chip determines the hologram that is written into the photorefractive crystal, this hologram being a function of the control of the reflective state of the liquid crystal, as this reflective state is in turn controlled by control of the VLSI chip.
The above references are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.